A flush valve assembly of the type disclosed herein is utilized with water closet combinations comprising a bowl and a reservoir tank. When such a water closet combination is installed, the bowl is first affixed to the floor and the tank is then supported directly on the bowl in such a way that a flow conduit is provided from the tank to the bowl in order to effect the flush. A seal must be effected between the bowl and the tank to prevent undesirable leakage of flush fluid, normally water, and a valving mechanism must be provided along the flow conduit selectively to control the flow of water from the tank into the bowl. This valve must be capable of effectively closing the flow from the tank to the bowl; must be easily operated; must remain open only until the water reservoir in the tank has been evacuated during the flushing operation; and, must then quickly and efficiently close.
Historically, the flush valve employed a sealing element that was movable into and out of engagement with a seat presented from the tank. Some such sealing elements were movable vertically and some were swung arcuately between their open and closed positions. Vent and overflow tubes were separately provided in these historic configurations. A marked improvement over the early, prior art was provided when the flush valve combined the sealing, vent and overflow functions into a single assembly. Representative of that advance in the prior art are the valve assemblies disclosed in such prior U.S. patents as that to Fulton et al, No. 3,172,129, and that to Snyder et al, No. 3,267,491.
The coupled functions incorporated in such prior art valve assemblies provide a relatively compact arrangement of the components in the reservoir tank of the water closet, which permits a smaller reservoir tank to be employed.
As well as these coupled assemblies work, they do require a sealing element in the nature of a diaphragm of rather intricate cross-sectional configuration. The cost to manufacture such diaphragms, because of their configuration, has continuously increased over the years.